Why Math.Ceiling returns double?

Question

In C# the method Math.Ceiling returns a double value. Why does it not return int?

Answer 1

Math.Ceiling can return either a double or a decimal, depending on the type passed in. In other words, the output type of the method matches the input type (quite sensibly).

They could have added a third overload that takes an int and returns an int, but there wouldn't have been much point to this - the function would always just return its input.

You seem to be assuming that the purpose of Math.Ceiling is to cast a floating-point value to an integer, but that's usually not how it's used.